Table of Contents
Advertisement
3 Electromagnetic Compatibility (EMC)
Information
3.1 Electromagnetic Interference (EMI) From Radio
Frequency Sources
Powered wheelchairs and motorized scooters (in this text, both
will be referred to as mobility devices) may be susceptible to
electromagnetic interference (EMI), which is interfering
electromagnetic energy (EM) emitted from sources such as
radio stations, TV stations, amateur radio (HAM) transmitters,
two way radios, and cellular phones. The interference (from
radio wave sources) can cause the mobility devices to release
its brakes, move by itself, or move in unintended directions. It
can also permanently damage the mobility devices control
system. The intensity of the interfering EM energy can be
measured in volts per meter (V/m). Each powered mobility
device can resist EMI up to a certain intensity. This is called its
"immunity level." The higher the immunity level, the greater
the protection. At this time, current technology is capable of
achieving at least a 20 V/m immunity level, which would
provide useful protection from the more common sources of
radiated EMI.
60101916-A
There are a number of sources of relatively intense
electromagnetic fields in the everyday environment. Some of
these sources are obvious and easy to avoid. Others are not
apparent and exposure is unavoidable. However, we believe
that by following the warnings listed below, your risk to EMI will
be minimized.
The sources of radiated EMI can be broadly classified
into three types:
1. Hand-held Portable transceivers (transmitters/receivers
with the antenna mounted directly on the transmitting
unit. Examples include: citizens band (CB) radios, "walkie
talkie", security, fire and police transceivers, cellular
telephones, and other personal communication devices).
Some cellular telephones and similar devices
transmit signals while they are ON, even when
not being used.
2. Medium-range mobile transceivers, such as those used in
police cars, fire trucks, ambulances and taxis. These usually
have the antenna mounted on the outside of the vehicle.
3. Long-range transmitters and transceivers, such as
commercial broadcast transmitters (radio and TV
broadcast antenna towers) and amateur (HAM) radios.
3 Electromagnetic Compatibility (EMC) Information
15
Advertisement
Table of Contents
